One of the things that CRV (Coastal Range Vineyards) told me early on is that after the first growing season, they will prune back the vines to one small trunk with only a couple of buds.  I knew it was coming, but it still was a little hard to see them cut back the vines that, in some cases, had reached all the way to the top wire.  The reason for this is to cut back the trunk so that the vine can concentrate all of its energy into the trunk and roots again for the second growing season.  This should allow the trunk of the vine to grow thicker, which will allow more sap flow, and more healthy growth in future years.